Twin laser camera assembly

ABSTRACT

A twin laser camera unitary assembly for a robot processing tool is disclosed. The assembly has a housing having a front wall defining an upright U-shaped channel into which a tubular portion of the tool is laterally insertable. A mounting support attaches the housing relative to the tool in operative position. Twin laser range finders are respectively mounted in the housing on opposite sides of the U-shaped channel in a symmetrical in-line arrangement with respect to the tool. A controller mounted in the housing is configured to receive robot control signals, operate laser projectors and process image signals produced by imagers of the laser range finders so that joint and bead position and geometry signals are produced in a robot reference frame. The assembly is designed and protected for use in industrial processes such as robotic laser and arc welding and sealant dispensing.

TECHNICAL FIELD

The present invention relates to robot material processing and moreparticularly to a twin laser camera assembly for a robot processing toolsuch as a welding torch or a sealant dispenser.

BACKGROUND INFORMATION

In order to perform real-time inspection of robotic welding, it is veryuseful and even sometimes required to also perform in-line jointmeasurement to obtain real-time data on joint location and geometry.These data are then used to compute the location and dimension of theweld bead relative to the joint or seam location and to extract the weldbead for precise weld inspection and detection of possible defects. Atthe present time, two separate standard laser cameras are mounted on arobot arm equipped with a welding torch as shown for example in WO2017/137550 (Schwarz et al.) and in U.S. Ser. No. 10/166,630 (Schwarz).One camera is used for joint tracking purposes, and the other one isused for weld bead inspection purposes. Such an arrangement of camerashas many drawbacks. For example, their mounting is problematic due tospace and process constraints around the welding torch. It is alsodifficult to position them symmetrically with respect to the weldingtorch for welding in both forward and backward directions. A standardcamera used for the inspection purpose must be located at a distancefrom the welding torch, e.g. 50-60 mm, to leave time for the cooling andsolidification process. As a result, the arrangement may require 310 mmor more space around the welding torch. Furthermore, two separatecameras require as many electronic control boards, electric cables andair supply tubes for camera nozzle cooling and protection. As they areseparate, each camera must have an absolute spatial calibration and asteady behavior over long operating periods on the robot arm, which isvery difficult to achieve.

Known in the art is DE 10 2014 104 031 A1 (Hofts et al.) which disclosesa process tracking and monitoring device for a robot. The device has amotorized round body defining a center hole for receiving an arm of therobot. The body has an upper fixed structure and a lower movablestructure. Two cameras and two light generators projects under themovable structure. A motor mounted in the body allows rotation of themovable structure and revolving of the cameras and light generatorsaround the arm of the robot for tracking and monitoring purposes. Thebody construction with fixed and movable structures complicates theassembly and the offside positioning of the light generators and camerasslows down the tracking and monitoring of the device. It is alsoquestionable that the construction could be used in harsh environmentslike robot welding where spatter and fumes emanate from a processedworkpiece.

Also known in the art is U.S. Pat. No. 6,541,757 (Bieman et al.) whichdiscloses a detection assembly for detecting dispensed material on aworkpiece. A ring of sensors is provided around the round housing of thedetection assembly. As in Hafts et al., the housing defines a centralopening through which a process tool extends so that the sensors andlight sources used to illuminate the workpiece and the dispensedmaterial surround the process tool. Again, it is also questionable thatthe design could be used in harsh environments like robot welding.

SUMMARY

An object of the invention is to provide a twin laser camera assemblyfor a robot processing tool which is compact, robust and versatile andmay be used for joint measurement and tracking and bead measurement andinspection in forward or backward directions, or for other robotizedprocesses where measurements, tracking and inspection may be needed.

According to one aspect of the present invention, there is provided atwin laser camera unitary assembly for a robot processing tool,comprising:

a housing having a front wall defining an upright opening into which aportion of the robot processing tool is laterally insertable;

a mounting support for attachment of the housing relative to the robotprocessing tool in an operative position where the portion of the robotprocessing tool extends in the upright opening and a tool center pointthereof projects under the housing;

first and second laser range finders respectively mounted in the housingon opposite sides of the upright opening in a symmetrical in-linearrangement with respect to the tool center point and a direction ofdisplacement thereof when in said operative position, the laser rangefinders respectively having laser projectors for projecting laser beamscrosswise to the direction of displacement of the robot processing toolat similar but opposite look-ahead and look-back distances from the toolcenter point of the robot processing tool, and corresponding imagerswith fields of view respectively over target areas at the look-ahead andlook-back distances where the laser beams are projected; and

an onboard controller mounted in the housing and connected to the laserrange finders, the onboard controller configured to receive robotcontrol signals, operate the laser projectors and process image signalsproduced by the imagers so that joint and bead position and geometrysignals are produced in a robot reference frame with respect to thedirection of displacement of the robot processing tool.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of preferred embodiments will be given hereinbelow with reference to the following drawings:

FIG. 1 is a schematic perspective view of a twin laser camera assemblyaccording to the invention.

FIG. 2 is a schematic cross-sectional view of a twin laser cameraassembly according to the invention.

FIG. 3 is another schematic perspective view of a twin laser cameraassembly according to the invention.

FIG. 4 is another schematic cross-sectional view of a twin laser cameraassembly according to the invention, showing internal electronic andoptical parts in more details.

FIG. 5 is another cross-sectional view of a variant of a twin lasercamera assembly according to the invention.

FIG. 6 is a schematic diagram of a robotic system using a twin lasercamera assembly according to the invention.

FIG. 7 is a schematic block diagram of an onboard controller andcomponents of a twin laser camera assembly according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used in connection with this disclosure, the expression “unitaryassembly” represents an assembly made of a single piece or a unifiedpiece made of a number of pieces put together in an assemblage, so thatthey act as one.

Referring to FIG. 1, there is shown a twin laser camera unitary assembly2 according to the invention, mounted relative to a robot processingtool 4 as a GMAW (gas metal arc welding) torch used to process aworkpiece 6. The assembly 2 comprises a housing 8 having a front walldefining an upright opening 10 U-shaped channel 10 into which a portion12 of the robot processing tool 4 is laterally insertable. The uprightopening 10 may be in the form of a U-shaped channel extending betweenupper and lower walls 61, 63 (as shown in FIG. 2) of the housing 8. Amounting support 14 is provided for attachment of the housing 8 relativeto the robot processing tool 4 in an operative position where theportion 12 of the robot processing tool 4 extends in the upright opening10 and a tool center point (TCP) 32 (or tip) of the robot processingtool 4 projects under the housing 8, as in the illustrated case.

Referring to FIG. 2, first and second laser range finders 16, 18 arerespectively mounted in the housing 8 on opposite sides of the uprightopening 4 in a symmetrical in-line arrangement with respect to the toolcenter point 32 and a direction of displacement of the robot processingtool 4 when in the operative position, as along axis X as shown inFIG. 1. The laser range finders 16, 18 respectively have laserprojectors 20, 22 for projecting laser beams 24, 26 crosswise to thedirection of displacement of the robot processing tool 4 at similar butopposite look-ahead and look-back distances 28, 30 from the tool centerpoint 32 of the robot processing tool 4, and corresponding imagers 34,36 with fields of view 38, 40 respectively over target areas at thelook-ahead and look-back distances 28, 30 where the laser beams 24, 26are projected. The laser beams 24, 26 are preferably projected in avertical plane of the assembly 2 and the fields of view 38, 40 aredirected from locations near the robot processing tool 4 for bettercompactness of the assembly 2, e.g. a size of 148 mm in the direction ofdisplacement of the robot processing tool 4.

A controller 42 is mounted in the housing 8 and connected to the laserrange finders 16, 18. The controller 42 is configured to receive robotcontrol signals e.g. through a cable connector 44 outwardly projectingfrom a wall of the housing 8 and connected to the controller 42, operatethe laser projectors 20, 22 and process image signals produced by theimagers 34, 36 so that joint and bead position and geometry signals areproduced in a robot reference frame with respect to the direction ofdisplacement of the robot processing tool 4. As a result, the joint 62and bead 58 geometries can be computed at the same location, such as atthe TCP 32.

The laser beam 24 projected at the look-ahead distance is a jointmeasurement laser beam and the laser beam 26 projected at the look-backdistance 30 is a bead measurement laser beam. The joint measurementlaser beam 24 may be used for joint inspection and/or joint trackingpurposes while the bead measurement laser beam 26 may be used for beadinspection purposes. In an embodiment, the controller 42 has a samepreset calibration for both laser range finders 16, 18, the imagesignals being processed by the controller 42 as a function of the presetcalibration. As a result, the functions of the laser range finders 16,18 may be swapped by the controller 42 so each laser range finder 16, 18can do both in-line tracking and inspection tasks depending on thedirection of displacement of the robot processing tool 4.

In an embodiment, each laser projector 20, 22 has a laser source 80, 82optically coupled to a lens 64, 70 extending in the bottom wall 63 ofthe housing 8, and each imager 34, 36 has an image sensor 84, 86 as e.g.a CMOS sensor optically coupled to a lens 66, 68 extending in the bottomwall 63 of the housing 8 through a mirror 88, 92 and lens 90, 94arrangement in order to sense a laser line resulting from the laser beam24, 26 projected on the workpiece 6.

In an embodiment, the upright opening 10 has an opening size in thehousing 8 so that the portion 12 of the robot processing tool 4 extendswithout contact in the upright opening 10 when the housing 8 is in theoperative position, for electrical insulation purposes.

Referring back to FIG. 1, the housing 8 and the mounting support 14 arepreferably made of aluminum. Other materials may be used if desiredprovided that they are adapted to the environment and use of theassembly 2 and that the mounting support 14 has enough stiffness toprevent the housing 8 from moving with respect to the robot processingtool 4. In an embodiment, the mounting support 14 has an elongated arm16 having an upper end provided with a flange 46 for attachment to anupper coupling structure 48 of the robot processing tool 4 that wouldusually be attached to a wrist of a robot arm (not shown) e.g. withbolts 47 and a dowel pin 49, and a lower end from which the housing 8projects. The elongated arm 16 has a form and a size determinative ofthe operative position of the housing 8 with respect to modelspecifications of the robot processing tool 4. Thus, different forms andsizes of elongated arms may be provided to accommodate different robotprocessing tools without any extra adjustments. Each elongated arm 16may thus be specific to a robot processing tool 4 and may bepre-calibrated for exact robot calibration of the twin laser cameraassembly 2 for a given robot processing tool 4.

Referring to FIG. 3, in an embodiment, the assembly 2 is preferablyprovided with a video camera 50 attached to the housing 8 and connectedto the controller 42 (as shown in FIG. 2). The video camera 50 has afield of view 52 (as shown in FIG. 1) over a target area including thetool center point 32 and at least one of the laser beams 24, 26. Thecontroller 42 (as shown in FIG. 2) is configured to receive an imagesignal from the video camera 50 and calibrate the tool center point 32based on the image signal from the video camera 50. The video camera 50may have an autofocus function and an optical input 52 provided with aprotective shutter 54 (as shown in FIG. 7) controllably openable andclosable by the controller 42. In an embodiment, the assembly 2 isprovided with a temperature sensor 56 (as shown in FIG. 7) attached tothe housing 8, possibly combined with the video camera 50, andpositioned for measurement of a temperature in at least one of thetarget areas, the controller 42 having an input for receiving atemperature signal from the temperature sensor 56 and configured toprocess the temperature signal according to the target area(s) monitoredby the temperature sensor 56, for example to measure the temperature ofa bead 58 (as shown in FIG. 1) resulting from the processing achieved bythe robot processing tool 4. In an embodiment, the assembly 2 is furtherprovided with an inertial measurement unit (IMU) 60 (as shown in FIG. 7)mounted in the housing 8 for measuring pitch and roll angles of thehousing 8, the inertial measurement unit 60 being connected to thecontroller 42 that may then be configured to determine orientations ofthe robot processing tool 4 and of a joint 62 (as shown in FIG. 1)tracked by the laser range finder 16, 18 operating at the look-aheaddistance 28 (as shown in FIG. 2). In an embodiment, the housing 8 isprovided with an insulated bracket 78 attachable to the lower end of themounting support 14 (as shown in FIG. 1) for electrical insulationpurposes with respect to the robot arm (not shown). The housing 8 mayhave an air inlet 96 outwardly projecting from a wall of the housing 8,connectable to a compressed air hose (not shown) in the case where thehousing 8 is provided with a protective nozzle 98 extending under thehousing 8, in communication with the air inlet 96, as disclosed in U.S.Pat. No. 9,541,755 (Boillot et al.).

Referring again to FIG. 2, in an embodiment, the bottom wall 63 definesin-line openings provided with lenses 64, 66, 68, 70 for passage of thelaser beams 24, 26 and receiving light in the fields of view 38, 40 fromthe target areas, the openings with the lenses 64, 70 for passage of thelaser beams 24, 26 being farther from the U-shaped channel 10 than theopenings with the lenses 66, 68 for receiving light from the targetareas. In an embodiment, the housing 8 is provided with protection flaps72, 74 downwardly projecting from the bottom wall 63 between theopenings with the lenses 64, 66, 68, 70 and the robot processing tool 4when the housing 8 is in the operative position. Such protection flaps72, 74 may advantageously provide shielding for the lenses 64, 66, 68,70 against welding light, fumes and spatter. The protection flaps 72, 74may be made of a single bent piece having a lower widened openingforming a chimney for enhanced evacuation of welding fumes through theU-shaped channel 10. In an embodiment, the housing 8 is provided with aninsulated plate 76 extending under the bottom wall 63 and surroundingthe U-shaped channel 10.

Referring to FIG. 4, the housing 8 may have a one-piece frame 100 ontowhich the components of the laser range finders 16, 18 and thecontroller 42 are mounted. Other components as the IMU 60 may also bemounted onto the frame 100. The frame 100 may advantageously be made ofaluminum and the housing may be machined for air cooling of the laserprojectors 20, 22, the imagers 34, 36 and the controller 42. Theassembly 2 thus has excellent dimensional stability.

Referring to FIG. 5, in the case where the robot processing tool 4 is amaterial dispenser as a sealant dispenser or a tool that does notproduce much heat or possible optical interferences, the positions ofthe laser projectors 20, 22 and the imagers 34, 36 of the laser rangefinders 16, 18 in the housing 8 may be swapped. The openings e.g. withlenses 64, 70 for passage of the laser beams 24, 26 are then closer fromthe U-shaped channel 10 than the openings e.g. with lenses 66, 68 forreceiving light 38, 40 from the target areas. As a result, thelook-ahead and look-back distances 28, 30 can advantageously be shorter,e.g. of 30 mm, to make it easier to follow sharp curve paths.

Referring again to FIG. 1, the assembly 2 according to the invention hasa compact U-shaped design for in-line tracking and inspection andpreferably integrates all the functions for forward and backward weldingor other processing. Both imagers 34, 36 (as shown e.g. in FIG. 2) mayshare a common optical reference frame and may be spatially calibratedin the robot TCP frame with a dedicated calibration target plate (notshown). The design of the assembly 2 greatly simplifies robotprogramming, improves accessibility and reduces cycle time byeliminating rotation of the robot wrist (not shown) to performinspection of the bead 58. Other advantages of the assembly 2 are itseasy mounting in operative position relative to a robot processing tool,shorter look-ahead and look-back distances, appropriate protectionagainst electric arcs, heat, fumes, spatter, one calibration for bothlaser range finders 16, 18, preset calibration features by the mountingsupport 14 with respect to the robot processing tool or the robot wrist,easy tool center tip calibration with the video camera 50, savings anddata processing efficiency with a single controller 42. The laserprojectors 20, 22 and the controller 42 can be adapted to implementnon-eye-safe and eye-safe operating modes as disclosed in U.S. Ser. No.10/043,283 (Boillot et al.), e.g. with red or blue laser sourcesdepending on the operation mode.

Referring to FIG. 6, a schematic diagram of a possible system using theassembly 2 according to the invention is shown. The laser range finder16 may be used to provide joint position data in 3D robot coordinates,basic joint tracking data with detected breakpoints and basic jointgeometry data before the welding (or other process). The laser rangefinder 18 may be used to provide bead position data in 3D robotcoordinates and bead geometry data. The data from the laser rangefinders 16, 18 may be transmitted to a joint measurement module 105 anda bead measurement module 106 that may be implemented in a laser visionsoftware executed by the controller 42 (as shown e.g. in FIG. 7) of theassembly for computing and providing the inspection or tracking data.Both modules 105, 106 may share tracking and inspection data that theyprocess through a link 122. A robot controller 108 may provide TCP datato the modules 105, 106 so that the tracking and inspection data can betransformed in 3D robot coordinates. The joint measurement module 105may implement program code that provides the robot controller 108 withthe tracking data as needed for joint tracking purposes and robot armoperation. The bead measurement module 106 may implement program codethat provides the robot controller 108 with the inspection data asneeded for adjusting the welding process and robot parameters accordingto preset weld characteristics and quality. The system thus hascalibrated coordinated tracking and inspection data that improve beadinspection with respect to reference data representing an unprocessedprofile, which allows extracting bead geometry data. The communicationsbetween the robot controller 108, the components of the assembly 2 and aPC station that may be used e.g. for process monitoring and databasestorage may advantageously be achieved through a common GigE (gigabitEthernet) link. Examples of front channel measurement data used in thesystem are a joint position (tracking point), joint geometry includinggap, mismatch, area, normal vector and path tangent vector possiblyenhanced with real-time knowledge of the robot position, adaptivewelding (or other process) parameters including position offsets,welding current and voltage, weaving, travel speed and wire-feed speedpossibly adjusted as a function of data feedback from back channelmeasurement data such as bead geometry to optimize the weldingparameters. Examples of the back channel measurement data that can beused in the system are a weld bead position in reference to unweldedjoint position, a weld bead geometry including width, height, leg sizes,undercuts, convexity, and possibly other geometric features, and endresults of the applied welding parameters that may help in computing theadaptive welding parameters. The bead position and geometry may beenhanced with real-time knowledge of the robot position, which may beused by the PC station 110 to build a 3D surface map representing thegeometry of the workpiece. These features may also be adjusted as afunction of data feedback from the front channel measurement data suchas joint position prior to welding since both laser range finders 16, 18share the same calibration 17, and an amount of material deposited onthe workpiece may be determined. Examples of data acquired from therobot controller 108 are current robot tool position/orientation (TCPdata), path or trajectory information computed from time-based evolutionof TCP data, synchronization control data e.g. for laser control, taskselection, tracking start/stop, inspection start/stop, welding direction(forward or backward), and process-related data e.g. process start/stopsignals, welding parameters, etc. Examples of data transmitted to therobot controller 108 are joint position in robot coordinates foraccurate positioning of the robot processing tool 4 for following thejoint, optimized welding parameters based on the joint and beadgeometries in the front and back channel measurement data, workpiecequality status e.g. pass, warning, fail or non-conforming geometry, anda list of possible defects e.g. types, sizes and positions).

The spatial positions of the laser range finders 16, 18 and the camera50 (as shown e.g. in FIG. 1) are calibrated in the same mechanicalreference frame 17 of the assembly 2. A calibration process used inorder to determine the relationship between the assembly 2 and the robot(not shown), may be carried out with multiple motions of the robot andmeasurements of the assembly 2 over a target plate (not shown), therelationship being computed as a function of the measurement dataprovided by the laser range finders 16, 18 with respect to calibrationfeatures on the target plate. A robot-assembly reference frame may thenbe determined. For a given model of welding torch or other robotprocessing tool 4 (as shown e.g. in FIG. 1), the theoretical TCP wiretip position is known in the same reference frame as the assembly 2. Thefollowing process may be used to determine the real position of the TCP(e.g. wire tip for an arc welding torch or laser spot for a laserwelding torch) for any robot processing tool 4 in the robot-assemblyreference frame. Using a simple plane workpiece positioned horizontally,the robot moves the assembly 2 perpendicularly towards the planeworkpiece using the measurement data of the laser range finders 16, 18,according to a factory-made calibration for a specific robot processingtool 4. At this step, the IMU 60 (as shown in FIG. 7) may be calibratedbased on an accurate vertical positioning of the assembly 2 and thelaser lines projected by the laser range finders 16, 18. A contact ofthe TCP wire tip with the workpiece, as achieved by the robot using thecamera 50 and a wire tip shadow on the surface of the workpiece or usingfeedback of a touch sensor (not shown), or by a manual positioningperformed by an operator, allows determining the position (x,y,z) of theTCP with the laser range finders 16, 18 since the tool 4 isperpendicular to the plane of the workpiece, as validated by the laserline measurements and the camera 50. The x,y positions may be computedwith x=xo+mx z and y=yo+my z. The x,y values may be also referenced inthe assembly reference frame since the camera 50 is already calibratedin this reference frame. The calibration data may be saved in the robotcontroller 108. Another way of performing the robot-assembly calibrationis possible using only one of the laser range finders 16, 18 and twointersecting laser pointers (not shown). An intersection of the laserpointers provides a height position of the TCP. Then, one of the laserrange finders 16, 18 and the camera 50 provides x, y, z measurementdata. An inclination of the robot processing tool 4 may advantageouslybe used for wire tip contact/touch detection since it would be longerand more visible, manually or through the camera 50. The TCP can bevalidated by a proprietary calibration system (e.g. target, elongatedarm 16, robot and software). Another way of calibrating the TCP may bewith a simple edge or lap joint. In that case, the laser range finders16, 18 are used to measure y1-Z1 and y2-Z2 positions of the edges or lapjoint. The TCP may be positioned on an edge, so a TCPy position isdetermined. Then, with a 90° rotation of the assembly 2 around the axialdirection of the TCP, a positioning of the TCP at a straight line of thelap should produce no error for TCPx and TCPz. If needed, newmeasurements on a target plane may be performed. Yet another way ofperforming the robot-assembly calibration may be achieved by positioningthe camera 50 and the TCP over a crosshair target. After a rotation ofthe assembly 2 around the axial direction of the TCP, a center of thecrosshair target should not deviate in the image provided by the camera50 when the calibration is appropriate. If needed, an error minimizationprocedure may be conducted by the robot.

In an embodiment, an operation sequence for coordinated in-line adaptivewelding, joint tracking and weld bead inspection may be as follows. Anoperator of the robot positions the TCP wire tip at a weld startposition with the torch 4 and assembly 2 orientations perpendicular to asurface of the workpiece 6, as validated by the calibrated trackinglaser line and the IMU 60. The robot controller 108 acknowledges andsaves the weld start position. The robot is then set in an operatingmode for tracking and measuring a joint with the laser range finder 16or 18 used for that purpose depending on the direction of displacementof the welding torch 4, over a partial length of the joint, and acquiresthe following parameters: type of joint to be welded, joint orientation,workpiece thickness, bevel angle of the joint, root and face gap, etc.From these parameters and applicable material data, the assembly 2 orthe robot controller 108 computes best or preferred welding parametersfrom a look-up table or other scheme. Examples of the welding parametersthat may be computed are welding speed, current, voltage, wire feedrate, wire tip length stickout, welding torch and work angles, etc. Theoperator validates the welding parameters and starts the weldingprocess. The welding parameters may be changed during the adaptivewelding as a function of joint orientation and gap. The measured weldingparameters may be recorded live during the welding, such as the jointorientation and gaps, voltage, current, welding speed, wire feed rate,bead profile and position relative to joint, joint temperature in frontor/and behind the torch 4, etc. The weld joint and weld bead data may bemerged with robot position data so that the weld bead volume may bedetermined. Main weld features may be computed such as location offset,bead width, throat, convexity, undercut, porosity, spatter, etc. Weldinspection data and quality may be assessed based on weldingrequirements. Weld quality may be correlated with the welding processand joint geometry variability. The weld bead inspection and jointtracking data and other data such as correlation data may be stored in adatabase for statistical analysis, trending and process improvementpurposes.

In an embodiment, the robot controller 108 may have an inspectionresults link 112 with the bead measurement module 106 for receivinginspection data computed by the bead measurement module 106, an Ethernetsynchronization bidirectional link 114 with the assembly 2 forsynchronizing the robot and the assembly 2, a TCP data link 116 fortransmitting TCP related data to the assembly 2, a process databidirectional link 118 with the assembly for sharing processedinspection data, and a tracking data link 120 with the joint measurementmodule 105 for receiving tracking data computed by the joint measurementmodule 105. The bead measurement module 106 and joint measurement module105 may share feedback data with each other through a link 122 as thelaser range finders 16, 18 may be used as much as for tracking as forinspection purposes. In that respect, the laser range finders 16, 18both have links 124, 126, 128, 130 with the bead measurement module 106and the joint measurement module 105. Detailed inspection data such asjoint and bead geometry and complete vision data such as profile datamay be transmitted to the PC station 110 through links 132, 134 with theassembly 2.

Thus, the tracking and inspection data provided by laser range finders16, 18 to the controller 42 may be used for a better quality control ofrobotic welding or other processes, and may be used for other purposessuch as statistical analysis, trending improvement and processoptimization. Robot processing tool 4 and joint 62 angles andorientations a, R, y around axes X, Y, Z may be provided by the IMU 84.Bead 58 and process (e.g. welding) temperatures may be provided by thetemperature sensor 56. The welding or other process parameters may becomputed by the controller 42 from a look-up table, workpiece dataspecifications and joint orientation for adaptive process control. Beadgeometry extraction from both joint and bead profile geometrical datamay be performed by the controller 42. Process start and end positionsmay be determined from operation of a power supply function in aninterface board 104 (as shown in FIG. 7). In the case of welding with afiller wire, control of weld convexity through filler wire and weldingspeed and control of weld penetration and dilution with wire additionrate versus weld convexity may be performed. The robot processing tool 4may be an arc welding torch, a laser welding torch, a brazing tool, etc.The controlled adaptive process or welding may be carried out in threedifferent modes: open loop, closed loop and self learning. In open loopmode, the twin laser camera assembly 2 measures the joint 62 and theonboard controller is configured to compute operating parametermodifications improving bead profiles based on measured data derivedfrom the bead position and geometry signals and a predetermined database(not shown) and then to transmit the operating parameter modificationsto a robot controller in an open loop. In closed loop mode, the onboardcontroller 42 is configured to transmit operating parametermodifications improving bead profiles to a robot controller, to measureresulting bead parameters and transmitting back new operating parametermodifications based on measured bead geometry to the robot controller ina closed loop. In self-learning mode, the onboard controller 42 isconfigured to use an artificial intelligence learning process in thesuccessive measurements of joint and bead geometry to determine bestoperating parameters providing predetermined bead profile and qualityand avoiding robot processing defects. The operating parameters may alsobe directly transmitted to a welding power source (not shown) ifdesired.

Referring to FIG. 7, a possible embodiment or configuration of thecircuits, functions and components of the assembly 2 is illustrated. AnEthernet 10/100/1000 bidirectional communication interface link 136 maybe implemented between the cable connector 44 and the interface board104. A 24 VDC input 138 may also be provided for chip and circuitpowering purposes. Also, a laser safety interlock input line 140 may beprovided if such a desirable function is implemented in the system. Theinterface board 104 may be provided with components and circuits forproviding power supply, status LED control, FPGA non-volatile memory,GigE magnetics, and laser interlock functions. The interface board 104may control a laser-on LED 142 (e.g. yellow) and a status led 144 (e.g.multi-color) through lines 146, 148. The interface board 104 may alsocontrol the laser sources 80, 82 through lines 150, 152, 154, 156provided with protection boards 158, 160. The controller 42 may have aFPGA board 162 connected to the interface board 104 through a bus 164.The FPGA board 162 may have lines 166, 168, 170, 172, 174 forcommunication with the image sensors 84, 86, the camera 50, the shutter54, the IMU 60 and the temperature sensor 56, e.g. in the form offlexible cables or a SPI (serial peripheral interface) cable. The FPGAboard 162 may have input lines 178, 180 for receiving signals fromprotective lens detection sensors 182, 184 intended for the protectivenozzle (as shown e.g. in FIG. 2). The FPGA board 162 may be programmedfor performing or providing image sensor interface functions, 3D profilegeneration, laser control, temperature monitoring, protective lensdetection, GigE PHY (physical layer of an open systems interconnectionmodel) interfacing, and IMU interfacing. A CPU board 186 may beconnected to the FPGA board 162 through a bus 188 to provide variouscomputational functions and others such as 3D profile calibration,vision processing, tracking control, inspection processing and robotinterface functions. A RTC (real-time clock) battery board 190 may beconnected to the FPGA board 162 through a signal line 192 to providee.g. timing functions for the controller 42.

While embodiments of the invention have been illustrated in theaccompanying drawings and described above, it will be evident to thoseskilled in the art that modifications may be made therein withoutdeparting from the invention. Modifications and substitutions by one ofordinary skill in the art are considered to be within the scope of thepresent invention, which is not to be limited except by the allowedclaims and their legal equivalents.

1. A twin laser camera unitary assembly for a robot processing tool,comprising: a housing having a front wall defining an upright openinginto which a portion of the robot processing tool is laterallyinsertable; a mounting support for attachment of the housing relative tothe robot processing tool in an operative position where the portion ofthe robot processing tool extends in the upright opening and a toolcenter point thereof projects under the housing; first and second laserrange finders respectively mounted in the housing on opposite sides ofthe upright opening in a symmetrical in-line arrangement with respect tothe tool center point and a direction of displacement thereof when insaid operative position, the laser range finders respectively havinglaser projectors for projecting laser beams crosswise to the directionof displacement of the robot processing tool at similar but oppositelook-ahead and look-back distances from the tool center point of therobot processing tool, and corresponding imagers with fields of viewrespectively over target areas at the look-ahead and look-back distanceswhere the laser beams are projected; and an onboard controller mountedin the housing and connected to the laser range finders, the onboardcontroller configured to receive robot control signals, operate thelaser projectors and process image signals produced by the imagers sothat joint and bead position and geometry signals are produced in arobot reference frame with respect to the direction of displacement ofthe robot processing tool.
 2. The twin laser camera unitary assemblyaccording to claim 1, wherein the laser beam projected at the look-aheaddistance is joint measurement laser beam and the laser beam projected atthe look-back distance is a bead measurement inspection laser beam, theonboard controller having a same preset calibration for both laser rangefinders, the image signals being processed by the onboard controller asa function of said preset calibration.
 3. The twin laser camera unitaryassembly according to claim 1, wherein the upright opening comprises aU-shaped channel extending between upper and lower walls of the housing.4. The twin laser camera unitary assembly according to claim 1, whereinthe upright opening has an opening size in the housing so that theportion of the robot processing tool extends without contact in theupright opening when the housing is in said operative position.
 5. Thetwin laser camera unitary assembly according to claim 1, wherein thehousing and the mounting support are made of aluminum.
 6. The twin lasercamera unitary assembly according to claim 1, wherein the mountingsupport has an elongated arm having an upper end provided with a flangefor attachment to an upper coupling structure of the robot processingtool, and a lower end from which the housing projects, the elongated armbeing pre-calibrated with a form and a size determinative of theoperative position of the housing with respect to model specificationsof the robot processing tool.
 7. The twin laser camera unitary assemblyaccording to claim 1, further comprising a video camera attached to thehousing and connected to the onboard controller, the video camera havinga field of view over a target area including the tool center point andat least one of the laser beams, the onboard controller configured toreceive an image signal from the video camera and calibrate the toolcenter point based on the image signal from the video camera.
 8. Thetwin laser camera unitary assembly according to claim 7, wherein thevideo camera has an optical input provided with a protective shuttercontrollably openable and closable by the onboard controller.
 9. Thetwin laser camera unitary assembly according to claim 1, furthercomprising a temperature sensor attached to the housing and positionedfor measurement of a temperature in at least one of the target areas,the onboard controller having an input for receiving a temperaturesignal from the temperature sensor and configured to process thetemperature signal according to said at least one of the target areas.10. The twin laser camera unitary assembly according to claim 1, furthercomprising an inertial measurement unit mounted in the housing formeasuring pitch and roll angles of the housing, the inertial measurementunit being connected to the onboard controller, the onboard controllerconfigured to determine orientations of the robot processing tool and ajoint measured by the laser range finder operating at the look-aheaddistance.
 11. The twin laser camera unitary assembly according to claim1, wherein the robot processing tool is a welding torch, and the housinghas a bottom wall defining in-line openings for passage of the laserbeams and receiving light from the target areas, the openings forpassage of the laser beams being farther from the U-shaped channel thanthe openings for receiving light from the target areas.
 12. The twinlaser camera unitary assembly according to claim 11, wherein the housingis provided with protection flaps downwardly projecting from the bottomwall between the openings and the robot processing tool when the housingis in said operative position.
 13. The twin laser camera unitaryassembly according to claim 11, wherein the housing is provided with aninsulated plate extending under the bottom wall and surrounding theupright opening.
 14. The twin laser camera unitary assembly according toclaim 11, wherein the housing is provided with an insulated bracketattachable to a lower end of the mounting support.
 15. The twin lasercamera unitary assembly according to claim 1, wherein the robotprocessing tool is a material dispenser, and the housing has a bottomwall defining in-line openings for passage of the laser beams andreceiving light from the target areas, the openings for passage of thelaser beams being closer from the U-shaped channel than the openings forreceiving light from the target areas.
 16. The twin laser camera unitaryassembly according to claim 1, wherein each laser projector has a lasersource optically coupled to a lens extending in a bottom wall of thehousing, and each imager has an image sensor optically coupled to a lensextending in the bottom wall of the housing through a mirror and lensarrangement.
 17. The twin laser camera unitary assembly according toclaim 1, wherein the housing has a cable connector outwardly projectingfrom a wall of the housing, the cable connector being connected to theonboard controller.
 18. The twin laser camera unitary assembly accordingto claim 1, wherein the housing has an air inlet outwardly projectingfrom a wall of the housing, the housing being provided with a protectivenozzle extending under the housing, the protective nozzle being incommunication with the air inlet.
 19. The twin laser camera unitaryassembly according to claim 1, wherein the housing has a main frame ontowhich the twin laser range finders and the onboard controller aremounted.
 20. The twin laser camera unitary assembly according to claim1, wherein the onboard controller is configured to compute operatingparameters adapting to measured joint geometry and to transmit theoperating parameters to a robot controller or a welding power source.21. The twin laser camera unitary assembly according to claim 1, whereinthe onboard controller is configured to compute operating parametermodifications improving bead profiles based on measured data derivedfrom the bead position and geometry signals and a predetermined databaseand then to transmit the operating parameter modifications to a robotcontroller in an open loop.
 22. The twin laser camera unitary assemblyaccording to claim 1, wherein the onboard controller is configured totransmit operating parameter modifications improving bead profiles to arobot controller, to measure resulting bead parameters and transmittingback new operating parameter modifications to the robot controller in aclosed loop.
 23. The twin laser camera unitary assembly according toclaim 22, wherein the onboard controller is configured to use anartificial intelligence learning process to determine best operatingparameters providing predetermined bead profile and quality and avoidingrobot processing defects.